assume cs:code

code segment

    start:      mov ax,2000H
                mov ds,ax
                mov bx,0

    s:          mov ch,0
                mov cl,ds:[bx]
                jcxz ok
                inc bx
                
                jmp short s

    ok:         mov dx,bx

                mov ax,4c00H
                int 21H

code ends
end start
